JACKSONVILLE — It has been a decade since former Gov. Jeb Bush joined forces with then-House Speaker John Thrasher to reduce taxes, legalize school vouchers and generally make life miserable for Florida's mostly liberal trial lawyers.

Having capitalized on that success by earning millions as a high-powered lobbyist, Thrasher now wants to return to the political arena, and Bush is the key. He stars in pro-Thrasher TV ads that blast the lawyers who are now aggressively working to defeat Thrasher.

With no Democrats running, the Sept. 15 primary for the North Florida Senate seat is winner-take-all where anything can happen, because voter turnout is usually low in special elections. That means a short, intense campaign heavy on advertising, and an effective get-out-the-vote effort can be crucial.

The result is a titanic and costly clash between the Republican old guard and trial lawyers, and the outcome could have implications for years in the state capital.

"John Thrasher had the courage to help me rein in frivolous lawsuits some lawyers depend on," Bush says in the new ad, calling the sustained attacks on Thrasher's integrity "wrong."

Because of those attacks, Thrasher's return to the Legislature is anything but assured.

Thrasher is one of four Republicans running for the Senate District 8 seat vacated by the death of Sen. Jim King on July 26.

The other candidates are Art Graham, a Jacksonville City Council member; Stan Jordan, a Duval County School Board member and former legislator; and Dan Quiggle, an antitax crusader and owner of a title company in Ponte Vedra Beach.

Through Friday, Thrasher had raised $325,000, more than his three rivals combined. But the dark-horse contender is Quiggle, who has 1,340 "friends" on his campaign Facebook page. Some polls show him pulling away.

"John Thrasher is an establishment Republican. Dan Quiggle is a movement conservative," said pollster Thom Eldon, who is watching the race and represents no candidate.

The battleground is an elongated vertical slice of northeast Florida stretching across five counties, anchored by Jacksonville, from the Georgia border south to Daytona Beach. The solidly Republican district has a sizable military presence: John McCain got 60 percent of the vote here in 2008.

The election will test the power of Bush's endorsement in a strongly Republican region. It is also a test of the influence of the trial bar, which has maintained its clout largely by supporting moderate Republican senators such as King and Ken Pruitt of Port St. Lucie, who resigned this summer.

While in office, the Thrasher-Bush pair threatened to cost trial lawyers lots of money by capping their fees and making it harder for them to sue businesses.

A Thrasher win would be bad news for lawyers because it would put the ex-speaker on the fast track to a leadership post in the Republican-led Senate.

A Thrasher defeat would strengthen the trial bar's clout and raise new questions about the value of a high-profile push from Bush.

The airwaves across Jacksonville are teeming with ads, most of them for or against Thrasher. One TV ad was paid for by Conservative Citizens for Justice, whose president, Tom Edwards, is the immediate past president of the Florida Justice Association, the lobbying arm of the trial bar.

The group's ad notes that Thrasher was twice criticized — reprimanded once and fined once — by the Commission on Ethics for violating lobbying restrictions.

A second group, Stop Tax Waste Inc., is flogging Thrasher in direct-mail fliers for spending $5.8 million to remodel the House chamber when he was speaker. President T.J. Harrington said his goal is to show voters that Thrasher is not the fiscal conservative he claims to be.

The criticism over the refurbishing has been aired so often that Thrasher felt compelled to defend himself at a meeting with Fernandina Beach residents.

He said the renovations were long overdue to make the chamber accessible to the disabled. He said no money was spent to improve the speaker's office, as the advertisement claims.

A Florida Retail Federation group is airing radio ads praising Thrasher, a Vietnam War veteran, as a conservative figure "fighting liberal interests." The Florida Chamber of Commerce's political group is airing TV ads that defend Thrasher by denigrating "greedy trial lawyers" in league with "illegal aliens."

The two other candidates both say they have the potential to ruin Thrasher's dream of a return to Tallahassee.

Jordan, 71, is a low-key politician and retired U.S. Army colonel and restaurant owner who says his deep ties to Jacksonville will overcome Thrasher's money.

He hosted a hot dog roast at an auto body shop on a weeknight that brought out nearly 200 people.

"This is the power brokers vs. the people," said Jordan, who championed military issues as a state House member from 2000 to 2008, when term limits forced him out and he was elected to return to the county School Board.

Quiggle, 40, is president of the Florida chapter of Americans for Prosperity and worked for a group affiliated with former President Ronald Reagan. A Quiggle flier, paid for by the pro-Quiggle Families for New Leadership, shows the candidate in two photos with the former president, and Quiggle is campaigning aggressively in opposition to Obama's health care plan. He is also active in antitax tea party rallies.

But the race appears to be a referendum on Thrasher, a 65-year-old lawyer who last week listed a worth of $7,475,678.

After leaving the House in 2000, he joined the powerhouse lobbying firm Southern Strategy Group. They parted ways last spring as Thrasher plotted a return to the Legislature.

Although Thrasher went to high school in Jacksonville, his political career is tethered to Clay County, to the southwest, which is outside the district. Thrasher bought a condo in St. Augustine, in the district, and is selling his Orange Park home.

When a woman at the rally in Fernandina Beach questioned Thrasher about his residency, he sounded defensive.